1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to video processing, and more particularly, to video processing which adjusts a brightness of a received video signal and displays a corresponding video.
2. Description of the Related Art
Generally, a video processing apparatus performs a predetermined process for a received video signal, and displays a video corresponding to the processed video signal. The processing apparatus may clearly display a video by adjusting the brightness of a concerned video signal. In particular, the video processing apparatus may display a dark area to be darker and a bright area to be brighter on the video so as to clearly display the video.
That is, the video processing apparatus may adjust the brightness of a concerned video according to a user input or a predetermined algorithm. Here, the predetermined algorithm may stretch a brightness of a specific portion of the video signal. For example, the predetermined algorithm may stretch a dark portion and a bright portion to adjust the brightness of the video signal. At this time, the predetermined algorithm may include a Black and White Stretch (BWS) algorithm.
Generally, if the video processing apparatus may adjust the brightness of a video signal and display a corresponding video, the brightness of the video signal includes its predetermined range capable of being processed and displayed by the video processing apparatus. The BWS algorithm indicates that if a brightness range of the input video signal is within its available range that the video processing apparatus can process and display, the video processing apparatus can clearly display a video corresponding to the input video signal through the BWS algorithm by stretching the brightness range to the available range.
Hereinafter, the BWS algorithm will be described with reference to FIGS. 1, 2A and 2B.
FIG. 1 is a block view illustrating a configuration of a conventional video processing apparatus to perform a BWS algorithm. As illustrated, a brightness stretching part 4 of the conventional video processing apparatus includes an average calculating part 4a, a stretch and gradient calculating part 4b, a histogram calculating part 4c, a maximum and minimum calculating part 4d, and a stretching performing part 4e. 
The average calculating part 4a calculates an average brightness value of a received video signal. If the average brightness value is calculated, the stretch and gradient calculating part 4b calculates a stretching point and a gradient to perform a stretching operation based on the calculated brightness average value. Here, the gradient indicates a rate of brightness change of an output video signal with respect to brightness change of an input video signal, and the stretching point indicates an arbitrary coordinate value on a line with a concerned gradient of a brightness coordinate plane of the input video signal and the output video signal to stretch a predetermined range between the stretching point and a brightness maximum or minimum value of the input video signal.
Separately from the calculating operation of the stretching point and the gradient, the histogram calculating part 4c calculates a brightness histogram for the received video signal. Then, the maximum and minimum calculating part 4d calculates a brightness maximum value and a brightness minimum value of the received video signal from the histogram calculated by the histogram calculating part 4c. 
In particular, as illustrated in FIG. 2A, the stretch and gradient calculating part 4b of the brightness stretching part 4 compares the average brightness value with respective brightness values of a preset black stretching point LB and a white stretching point UW. As the result of comparing, if the brightness value of the preset black stretching point LB is larger than the average brightness value, the stretch and gradient calculating part 4b sets up the average brightness value as a new black stretching point LB. Also, if the brightness value of the preset white stretching point UW is smaller than the average brightness value, the stretch and gradient calculating part 4b sets up the average brightness value as new white stretching point UW. Accordingly, if the black and white stretching points LB and UW are determined through the above-described comparing operation, the brightness stretching part 4 sets up a “BS” area and a “WS” area. Here, the “BS” area indicates an area having smaller brightness value than the black stretching point LB, and the “WS” area indicates another area having larger brightness value than the white stretching point UW.
Then, the stretching performing part 4e changes a gradient from BS1 to BS2 in the “BS” area, and from WS1 to WS2 in the “WS” area, by changing the previous gradients BS1 and WS1. Accordingly, the video processing apparatus can display a dark portion to be darker and a bright portion to be brighter on the video by stretching corresponding ranges of the dark and bright portions of the received video signal in order to emphasize the corresponding brightness contrast.
However, for example, if the BWS algorithm is performed by the brightness stretching part 4, and the brightness of the whole portion of the received video signal is adjusted, the stretching performing part 4e changes the gradient from BS1 to BS2 or BS3 in the “BS” area, and from WS1 to WS2 or WS3 in the “WS” area as illustrated in FIG. 2B.
At this time, since the conventional video processing apparatus adjusts the brightness of the whole portion of the received video signal, a brightness range of a specific portion (for example, a “B” portion and a “W” portion in FIG. 2B) of the received video signal is not suitably stretched by the BWS algorithm. Accordingly, the brightness of the received video signal corresponding to portions “B” or “W” cannot be suitably displayed.